Axially asymmetric metal alkyls. Part 4. Synthesis and X-ray crystal structure of the tungsten(V) metallabicyclic complex [{W[(2-CH2C6H4)2]2O}2Mg(C4H8O)4]·CH2Cl2

Abstract

Reaction of the di-Grignard reagent [{Mg(thf)_nCl}₂{(2-CH₂C₆H₄)₂}], derived from [Mg(anth)(thf)₃](anth = anthracene) and (2-CICH₂C₆H₄)₂, with WCI₄O in tetrahydrofuran (thf) yields a paramagnetic species, shown by an X-ray diffraction study to be [{W[(2-CH₂C₆H₄)₂]₂[graphic omitted]g(thf)₄]. Within each molecule the bidentate alkyl ligands have the same chirality, the overall molecular symmetry being approximately 222. A two-fold axis containing the oxo-groups and metal centres is the only crystallographically imposed symmetry. Oxo-groups are trans in the octahedrally co-ordinated magnesium centre [Mg–O(oxo) 2.036(5), 2.029(5)Å; Mg–O(thf) 2.080(3), 2.1 20(5)Å] and occupy an apical position of square-pyramidally co-ordinated tungsten centres [W–01.744(5), 1.726(4) A; W–CH₂ 2.162(5)–2.191(4)Å]. Important angles of the metallacycles are: CH₂–W–CH₂ 83.7(2), 85.8(2)°; W–CH₂ C(aryl)115.3(4)–121.1(4)°; and torsion angles along the biphenyl axes, 52.9 and 63.1°.